Comprehensive Machinability Assessment of Ti6Al4V Alloy During Drilling and Helical Milling Using Sustainable Dry Condition

Abstract

Cutting fluids are an essential requirement while machining materials like Ti6Al4V alloy exhibiting low thermal conductivity and work hardening behavior. However, the non-biodegradable nature of the oil increases carbon emissions and causes serious health concerns, thus jeopardizing sustainability. In addition, complexity increases when drilling Ti6Al4V alloy due to the temperature build-up, leading to material adhesion and accelerated tool wear. The study, therefore, investigates the utility of helical milling for creating holes in Ti6Al4V alloy. The hole-making operations were appraised considering the chip morphology, microhardness, machining temperature, tool wear, and surface roughness. The findings show that hole-making using helical milling was beneficial since it produced lower thrust force. Measured temperatures during helical milling were significantly lower than in drilling. Helically milled holes displayed superior quality holes with lower surface roughness; however, at higher productivity conditions, chatter marks were noted. The microhardness was lower near the machined surface in the case of conventional drilling, indicating material softening. In comparison, helical milled holes displayed higher microhardness very close to the edge of the hole due to work hardening. The helical milling operation produced short discontinuous chips, which are desirable while machining Ti6Al4V alloy. Furthermore, the examination of the cutting tool showed material adhesion. The severity of tool damage was significantly lower during the helical milling operation. The initial assessment indicates that helical milling is an adept process for making holes in Ti6Al4V alloy.